Chapter 04


Chapter Objectives

When Claims conflict

  • Understand that when a claim conflicts with other claims we have good reason to accept, we have good grounds for doubting it.
  • Recognize that if a claim conflicts with our background information, we have good reason to doubt it.
  • Appreciate that when we are confronted with a claim that is neither completely dubious or fully credible, we should proportion our belief to the evidence.
  • Realize that it's not reasonable to believe a claim when there is no good reason for doing so.

Experts and Evidence

  • Understand what makes someone an expert and what does not.
  • Understand that if a claim conflicts with expert opinion, we have good reason to doubt.
  • Realize that when the experts disagree about a claim, we have good reason to doubt it.
  • Be able to recognize fallacious appeals to authority.
  • Be able to distinguish true experts from nonexperts by using the four indicators of expertise.

Personal Experience

  • Understand that it's reasonable to accept the evidence provided by personal experience only if there's no good reason to doubt it.
  • Appreciate the importance of the common factors that can give us good reason to doubt the reliability of personal experience -- impairment, expectation, and innumeracy.

Fooling Ourselves

  • Appreciate why we need to resist the human tendency to resist contrary evidence.
  • Become sensitive to the possibility of confirmation bias.
  • Be alert to the possibility of the availability error.

Claims in the News

  • Have a basic understanding of how the news media work and what factors influence the claims that they generate.
  • Understand the skills involved in evaluating claims in the news.

Chapter summary


Many times we need to be able to evaluate an unsupported claim -- a claim that isn't backed by an argument. There are several critical thinking principles that can help us do this. An important one is: If a claim conflicts with other claims we have good reason to accept, we have good grounds for doubting it. Sometimes the conflict is between a claim and your background information. Background information is the large collection of very well supported beliefs that we rely on to inform our actions and choices. The relevant principle then is: If a claim conflicts with our background information, we have good reason to doubt the claim.
It's not reasonable to accept a claim if there is good reason to doubt it. In the case of claims that we can neither accept nor reject outright: We should proportion our belief to the evidence.
An expert is someone who is more knowledgeable in a particular subject area than most others are. The important principle here is: If a claim conflicts with expert opinion, we have good reason to doubt it. We must couple this principle with another one: When the experts disagree about a claim, we have good reason to doubt it. When we rely on bogus expert opinion, we commit the fallacy known as the appeal to authority.
Many claims are based on nothing more than personal experience, ours or someone else's. We can trust our personal experience -- to a point. The guiding principle is: It's reasonable to accept the evidence provided by personal experience only if there's no reason to doubt it. Some common factors that can raise such doubts are impairment (stress, injury, distraction, emotional upset, and the like), expectation, and our limited abilities in judging probabilities.
Some of the common mistakes we make in evaluating claims is resisting contrary evidence, looking for confirming evidence, and preferring available evidence. To counteract these tendencies, we need to take deliberate steps to critically examine even our most cherished claims, search for disconfirming evidence as well as confirming, and look beyond evidence that is merely the most striking or memorable.
Many of the unsupported claims we encounter are in news reports. Reporters, editors, and producers are under many pressures that can lead to biased or misleading reporting. The biggest factor is money -- the drive for profits in news organizations, especially those owned by larger corporations or conglomerates. Reporters themselves may introduce inaccuracies, biases, and personal opinions. And the people who produce the news may decide not to cover certain stories (or aspects of stories), which can sometimes provide a skewed or erroneous picture of an issue or event.
The best defense against being misled by news reports is a reasonable skepticism and a critical approach that involves, among other things, looking for slanting, examining sources, checking for missing facts, and being on the lookout for false emphasis.